This invention relates to motion detection circuits for extracting the motion information in the high definition television picture signal of the image reproduction devices based on the MUSE (multiple sub-Nyquist sampling encoding) signal.
FIG. 1 is a block diagram showing the typical structure of the conventional motion detection circuit for MUSE decoder. FIG. 2 is a diagram showing the sampling pattern of the luminance signal (Y-signal) for the MUSE (multiple sub-Nyquist sampling encoding) high definition television system. The frames of the picture signal are transmitted in cycles of four fields, upon the data transmission rate of 16.2 Mbps. In FIG. 1 and 2, the sampling points of the first and the second field are represented by white and black circles, respectively. The sampling points of the third and the fourth field are represented by white and black diamonds, respectively.
To the present data input terminal 1 is input the currently transmitted data (the present data). The edge detector circuit 3 detects the edge component (i.e., the components of high horizontal or vertical frequencies) or the high level component of the signal input to the present data input terminal 1. The edge detector circuit 3 converts the information into a signal at a data transmission rate twice as high as that of the input, i.e., to 32.4 Mbps, and supplies the output to the sensitivity converter circuit 6.
To the interframe interpolation data input terminal 2 is input the interframe interpolation data which consists of the present data (currently transmitted data) and the preceding frame data (the data that has been transmitted one frame earlier), wherein the preceding frame data are interpolated between the present data, such that the data transmission rate of the interframe interpolation data supplied to the interframe interpolation data input terminal 2 is at 32.4 Mbps.
The MUSE signal includes folding disturbance component (folding noise components) in the horizontal frequency region above 4 MHz (designated by .mu.0) for processing the still picture image. The horizontal filter 4 obtains the one interframe differential from the signal supplied to the interframe interpolation data input terminal 2, and limits the band width of the differential data to the frequency components under .mu.0.
The output of the horizontal filter 4 at the same data transmission rate, 32.4 Mbps, as the input thereto, is supplied to the vertical filter 5. The MUSE signal includes folding disturbance components (folding noise components) for the moving picture image processing procedure in the vertical frequency region in the neighborhood of 1125/4 (c/h), which is designated by .mu.0. The vertical filter 5 removes these disturbance components.
The output signal of the vertical filter 5 at the data transmission rate 32.4 Mbps is a one interframe differential data from which the folding disturbance components are removed. The output signal of the vertical filter 5 represents the motion information of the picture. However, the sensitivity thereof at the edge or the high level components is too high.
The sensitivity converter circuit 6 thus divides the output signal of the vertical filter 5 representing the motion information by the output signal of the edge detector circuit 3 representing the information upon the edge and the high level components, and thereby normalizes the sensitivity of the output signal of the vertical filter 5. Thus the motion information data with normalized sensitivity and at the data transmission rate of 32.4 Mbps is obtained at the motion detection data output terminal 7 supplied from the sensitivity converter circuit 6.
The above conventional motion detection circuit has the disadvantage that the motion information contained in components of horizontal frequency above .mu.0 cannot be obtained. Further disadvantage is that the edges of the motion detection data are blurred and become unclear.